There are a number of ways to prepare copper(II) chloride (cupric chloride). For example, the anhydrous salt can be obtained by electrolysis of a hydrochloric electrolyte with a copper anode or by chlorination of metallic copper at 400.degree.-500.degree. C. with exclusion of air.
The dihydrate can be prepared, for example, by dual reaction of copper(II) sulfate with sodium chloride in accordance with the process of French Pat. No. 754,184.
Processes using copper(II) oxychloride as starting material are of special interest industrially. This compound is readily available as copper ore and easily accessible from a technical viewpoint. By treating copper(II) oxychloride with aqueous hydrochloric acid, copper(II) chloride is directly obtained.
The reaction of copper(II) oxychloride to copper (II) chloride represents, for example, one step in an overall process involving oxychlorination. The latter process can be divided, for purposes here, into two partial steps. The usual procedure is to chlorinate an organic substrate, e.g., ethylene, using copper(II) chloride (1); oxidizing the resultant copper(I) chloride with atmospheric oxygen to obtain copper(II) oxychloride (2); and finally closing the copper cycle by reacting copper(II) oxychloride with hydrogen chloride to obtain copper(II) chloride (3). EQU 2CuCl.sub.2 +CH.sub.2 .dbd.CH.sub.2 .fwdarw.Cl--CH.sub.2 --CH.sub.2 --Cl+2CuCl (1) EQU 2CuCl+1/2O.sub.2 .fwdarw.Cu.sub.2 OCl.sub.2 ( 2) EQU Cu.sub.2 OCl.sub.2 +HCl.fwdarw.2CuCl.sub.2 +H.sub.2 O (3)
One disadvantage is that high-percentage hydrogen chloride is required in this process. The dilute aqueous hydrochloric acids obtained in many technical processes are unsuitable since, with their use, the resultant copper(II) chloride solution would have evaporated.
Moreover, it is known from European Patent Application 00 13 586 to utilize the hydrochloride of a volatile amine as a hydrogen chloride donor for the synthesis of copper(II) chloride. The amine hydrochloride is converted into the free amine with the aid of air in the presence of copper salts. Simultaneously, a transfer of chloride from hydrogen chloride to the olefin is brought about under the catalytic action of iodine added to the reaction mixture. The process exhibits the following substantial disadvantages:
1. The amine is obtained in the form of a strongly diluted gaseous mixture so that it must first be increased in concentration before reuse.
2. The amine is subject to oxidative decomposition phenomena during the oxidation of the hydrogen chloride and in the presence of iodine.